U.S. patent number 7,956,033 [Application Number 12/482,041] was granted by the patent office on 2011-06-07 for modified peptide of human acidic fibroblast growth factor.
This patent grant is currently assigned to Eu Sol Biotech Co., Ltd.. Invention is credited to Henrich Cheng, Wen-Chun Kuo.
United States Patent |
7,956,033 |
Cheng , et al. |
June 7, 2011 |
Modified peptide of human acidic fibroblast growth factor
Abstract
An modified peptide of human acidic fibroblast growth factor
(aFGF), comprising a native human aFGF shortened by a deletion of a
deletion of 20 amino acids from N-terminal of the native human
aFGF, and an addition of Alanine (Ala) before the shortened native
aFGF is provided.
Inventors: |
Cheng; Henrich (Taipei,
TW), Kuo; Wen-Chun (Taipei, TW) |
Assignee: |
Eu Sol Biotech Co., Ltd.
(Taipei, TW)
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Family
ID: |
41400867 |
Appl.
No.: |
12/482,041 |
Filed: |
June 10, 2009 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20090305988 A1 |
Dec 10, 2009 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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61060262 |
Jun 10, 2008 |
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Current U.S.
Class: |
514/9.1; 530/350;
530/399 |
Current CPC
Class: |
C07K
14/501 (20130101); A61K 38/00 (20130101) |
Current International
Class: |
A61K
38/18 (20060101); C07K 14/50 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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11 2005 000 737 |
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Apr 2007 |
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DE |
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2000236880 |
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Sep 2000 |
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JP |
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02/14471 |
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Feb 2002 |
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WO |
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WO 2005/095600 |
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Oct 2005 |
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WO |
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Primary Examiner: Allen; Marianne P
Attorney, Agent or Firm: Occhiuti Rohlicek & Tsao
LLP
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATION PARAGRAPH
This application claims the benefit of U.S. Provisional Application
No. 60/060,262 filed on Jun. 10, 2008, the content of which is
hereby incorporated by reference in its entirety.
Claims
We claim:
1. A modified peptide of human acidic fibroblast growth factor
(aFGF) consisting of the amino acid sequence of SEQ ID NO:1.
2. A pharmaceutical composition comprising the modified peptide of
claim 1 and a pharmaceutically acceptable carrier.
Description
FIELD OF THE INVENTION
The present invention is related to a modified peptide of acidic
fibroblast growth factor with a better stability.
BACKGROUND OF THE INVENTION
Acidic fibroblast growth factor (aFGF), which influences the
proliferation and differentiation of various cell types in vitro,
were originally isolated as single chain proteins from neural
tissue, including whole brain and hypothalamus. The aFGF is a
heparin-dependent mitogen and it can strongly bind on all four
known FGF receptors and their spliced form. It can be localized
within specific subsets of neurons associated with motor and
sensory functions, and can be purified from the adult brain.
Purified aFGF is a mitogen for neuroblasts and promotes the
neurites extension from spinal cord neurons.
Native peptide of human aFGF is isolated from human brain, and
consists of 154 amino acids. However, 19 amino acids in N-terminal
of the native human aFGF have been identified homogenous with human
interleukin-1 (IL-1). The similar domain of polypeptide between
human aFGF and IL-1 may cause the same endogenous immuno-response,
including activation of macrophages, and modulated cells growth
arrest (G. Venkataraman et al., P.N.A.S., 96:3658-63, 1999).
Furthermore, the pro-inflammatory cytokine IL-1 and FGF-1
(aFGF)/FGF-2 (bFGF) share the same structural scaffold and compete
against the same receptor binding site of tyrosine kinase domains
(A. J. Minter et al., J. Cell Physil., 167:229-37, 1996).
BRIEF SUMMARY OF THE INVENTION
The invention provides an modified peptide of human acidic
fibroblast growth factor (aFGF) named as aFGF135, comprising a
native human aFGF shortened by a deletion of a deletion of 20 amino
acids from N-terminal of the native human aFGF, and an addition of
Alanine (Ala) before the shortened native aFGF. In particular, the
peptide aFGF135 comprises the amino acid sequence of SEQ ID NO: 1,
which has a relatively high stability and is better than known aFGF
peptides.
The present invention further provides a pharmaceutical composition
comprising the peptide aFGF135 of the invention and a
pharmaceutically acceptable carrier.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing summary, as well as the following detailed
description of the invention, will be better understood when read
in conjunction with the appended drawings. It should be understood,
however, that the invention is not limited to the precise
arrangements and instrumentalities shown.
In the drawings:
FIG. 1A is an image of the western blotting showing the degradation
of the peptide aFGF135 after an incubation at 37.degree. C. during
a time period of 48 hours; wherein lanes 1 to 3 were the results
after 6-hour, 24-hour and 48-hour incubation, respectively, and
lane 4 was the molecular marker, and the number above each of the
bands represented the molecular weight.
FIG. 1B is an image of the western blotting showing the degradation
of the peptide aFGF135 after an incubation at 54.degree. C. during
a time period of 120 minutes (2 hours); wherein lanes 1 to 3 were
the results after 10 minutes, 60 minutes and 120 minutes
incubation, respectively, and lane 4 was the molecular marker, and
the number above each of the bands represented the molecular
weight.
FIG. 2 is an image of the western blotting showing a comparison
regarding the degradation between the peptide aFGF135 (shown as
lane "E") and a commercial human aFGF having 140 amino acids (as
lane "P") after an incubation at 54.degree. C. for one hour;
wherein lane "M" was the molecular markers and the degradation of
the commercial human aFGF was presented in lane P, which was noted
by a black arrow.
FIG. 3 is a diagram showing the .sup.1H--.sup.15N-HSQC spectrum of
the peptide aFGF135 detected by a liquid-state protein NMR
spectroscopy.
FIG. 4A is a 3D structure diagram of the peptide aFGF135 as
predicted according to the .sup.1H.sup.15N-HSQC spectrum as shown
in FIG. 3.
FIG. 4B is a 3D structure diagram of a human aFGF having 140 amino
acids under PDB Code 1RG8.
FIG. 4C is a 3D structure diagram of a human aFGF having 127 amino
acids under PDB Code 1DZD.
DETAILED DESCRIPTION OF THE INVENTION
This present invention provides an modified peptide of human acidic
fibroblast growth factor (aFGF) named as aFGF135, comprising a
native human aFGF shortened by a deletion of a deletion of 20 amino
acids from N-terminal of the native human aFGF, and an addition of
Alanine (Ala) before the shortened native aFGF. In particular, the
peptide aFGF135 comprises the amino acid sequence of SEQ ID NO: 1.
Unexpectedly, the modified peptide of the peptide aFGF135 has
relatively high stability under physiology of temperature and has a
distinct structure from other known aFGFs.
According to the invention, the peptide aFGF135 has the amino acid
sequence of SEQ ID NO: 1 with relatively high stability. As
compared with the native human aFGFs, the peptide aFGF135 has a
deletion of 20 amino acids from N-terminal of the native human aFGF
(called as "the shortened aFGF") and an addition of Alanine (Ala)
before the 20 a.a. deleted aFGF. According to the invention, the 20
amino acids were deleted from the native human aFGF to avoid the
IL-1-like effects via the common pathway because the first 19 amino
acids of human aFGF have been identified homogenous with human
interleukin-1 (IL-1), and were deleted. It was unexpectedly
discovered that the peptide aFGF has outstanding stability under
physiology of temperature, which is much better than known aFGFs,
including native human aFGF. As shown in the example of the
invention, the peptide aFGF135 was in the status of a correct
folding without denaturation or hydrolysis at body temperature
(such as about 37.degree. C.) for at least 48 hours of incubation
(as shown in FIG. 1A). In another example of the invention, the
peptide aFGF135 maintained its intact structure at a self
accelerating decomposition temperature (such as about 54.degree.
C.) for an one-hour incubation (as shown in FIG. 1B). Accordingly,
the peptide aFGF135 has a relatively high stability as compared
with known aFGFs, such as known human aFGFs having 140 amino acids
and 127 amino acids, respectively.
To show the distinctness between the peptide aFGF135 and the known
aFGFs, NMR spectrograph was used to calculate the actual structure
of the peptide aFGF135 in three-dimensions, and was compared with
known aFGFs.
As compared with a human aFGF having 140 amino acids under Protein
Data Bank (PDB) Code 1RG8 as published by Bernett M J et al.
(Proteins, 57(3):626-34, 2004) and a human aFGF having 127 amino
acids, PDB Code 1DZD as published by Lozano R M. Et al
(Biochemistry, 2; 39(17):4982-93, 2000), the peptide aFGF135 has a
different structural characterization, including C-terminal and
N-terminal exposing and a distinct binding loop down left as shown
in FIG. 4A. It suggests that the peptide aFGF with a modified
sequence (including a deletion of 20 amino acids and an addition of
Ala) causes a more stable structure than other known recombinant or
natural aFGF. In one example of the invention, a comparison
regarding stability in terms of degradation was conducted and the
commercial recombinant aFGF (Promega Corporaton) showed a
degradation band on the western blotting after a one-hour
incubation at 54.degree. C., but the peptide aFGF135 appeared
stable, as shown in FIG. 2.
The present invention further provides a pharmaceutical composition
comprising the peptide aFGF135 of the invention and a
pharmaceutically acceptable carrier.
The pharmaceutical composition of the present invention can be
manufactured by conventionally known methods with one or more
pharmaceutically acceptable carriers. The term "pharmaceutically
acceptable carrier" as used herein encompasses any of the standard
pharmaceutical carriers. Such carriers may include, but are not
limited to: saline, buffered saline, dextrose, water, glycerol,
ethanol and combinations thereof.
The pharmaceutical composition of the present invention may be
constituted into any form suitable for the mode of administration
selected. Preferably, the composition is applied to the surgery
area directly.
The present invention is further illustrated by the following
examples, which are provided for the purpose of demonstration
rather than limitation.
EXAMPLE 1
Cloning of the Peptide aFGF135
The full length of human aFGF was a product of Quick Clone cDNA
bought from Clontech Laboratories, Inc. Before the construct, two
specific primer sequences were designed as following:
TABLE-US-00001 SEQ ID NO: 2: 5'-ACTG.sup.AATTCATGGCTGAAGGGGAA
ATCA-3' SEQ ID NO: 3: 5'-AAGA.sup.AGCTTCATCAGA AGAGACTGGCAGG-3'
There was a EcoR1 restriction site in SEQ ID NO:2 (which is labeled
as .sup.), whereas a Hind III restriction site in SEQ ID NO:3
(which is labeled as .sup.). The full length product was used to
PCR amplification with the primers aforementioned, and a PCR
product of 485 base pairs was obtained. After the recombinant cDNA
reacted with restriction enzymes of EcoR1 and Hind III, the cut
fragment was inserted into pUC18vector which had the same
restriction sites.
According to the template of pUC-haFGF, two specific primer
sequences were designed as following:
TABLE-US-00002 SEQ ID NO: 4: 5'-GGCA.sup.TATGGCTAATTACAAGAAGCCC-3'
SEQ ID NO: 5: 5'-AAGA.sup.GATCTCTTTAATCAGAAGAGACTGGCA GG-3'
There was a Nde I restriction site in SEQ ID NO:4 (which is labeled
as .sup.), whereas a Bgl II restriction site in SEQ ID NO:5 (which
is labeled as .sup.). The length of cDNA amplified by SEQ ID NO:4
and SEQ ID NO:5 was shortened by 57 base pairs from full length.
The peptide aFGF135 had only 135 amino acids, and preserved the
major functional domain of aFGF. Moreover, the secondary amino acid
-Glycine (G) which was changed to Alanine (A) in N-terminal. It was
shown as: ANYKKPKLLY in SEQ ID NO: 1. The cDNA fragment amplified
by pUC18-haFGF was reacted with restriction enzymes of Nde I and
Bgl II, and the cut fragment was inserted into pET3c vector which
had the same restriction sites. As the result, a pET3c-haFGF was
constructed.
EXAMPLE 2
Expression and Isolation of the Peptide aFGF135
After amplifying pET3c-haFGF, the vector was transformed to DNA
with BL21(DE3) (Novagen, Germany) competent cell. The E. coli
colonies resistant to ampicillin were cultured and amplified in LB
medium to OD.sub.600=0.3 before induction with final concentration
of 1 mM IPTG (Isopropyl .beta.-D-1-thiogalactopyranoside). After
incubation for 16 hour (.+-.2 hour), bacteria were collected and
centrifuged with 27000.times.g to remove supernatant. The collected
bacteria were washed with PBS twice, then lysed with a high
pressure homogenizer (Niro Soavi model NS2006L, Daken Stainless
Products Ltd., UK). The lysed sample was flowed trough a sieve with
the pore size of 0.22 .mu.m and ready for isolation of protein.
The peptide of human aFGF135 was isolated by the of chromatography
as follows: (1) cation exchange chromatography (CMFF column, RM197,
GE Healthcare Bio-Sciences USA Corp.); (2) affinity chromatography,
which was specific to heparin (Heparin FF column, RM 244, GE
Healthcare Bio-Sciences USA Corp.); and (3) size exclusion
chromatography (Superdex 75 pre-grade column, RM245, GE Healthcare
Bio-Sciences USA Corp.). The buffer used for the aforementioned
columns was phosphate solution (Na.sub.2PO.sub.4:NaHPO.sub.3=51:49
with 0.1% EDTA-Na, pH 6.8-7.2). The final product as obtained was
the target peptide of the present invention. The molecule weight of
the peptide aFGF135 was 15281 Da as determined by LC-MSMS
assay.
EXAMPLE 3
Stability Test of the Peptide aFGF135
(I) Western Blotting Analysis
The crude peptides were subjected to SDS-PAGE in 4-20 or 10-20%
gradient gels and then transferred to nitrocellulose membranes
(0.05 .mu.m; Schleicher & Schuell, Inc., Keene, N.H.) by
electrophoresis' transfer (Polyblot Transfer System, Model
SBD-1000; American Bionetics, Emeryville, Calif.). To investigate
the stability of the aFGF peptides, Laemmli buffer (2.4 ml 1 M Tris
pH 6.8, 0.8 g SDS-stock, 4 ml 100% glycerol, 0.01% bromophenol
blue, 0.02% 1 ml .beta.-mercaptoethanol (electrophoresis grade),
and 2.8 ml water) with or without 8 M urea (to break up potential
aggregates) was prepared as a stacking gel buffer including 0.0625
M Tris-base, SDS stock 1%, and dithiothreitol 15 mM. The samples
were kept at room temperature for 1 h, then 4.degree. C. overnight.
It was boiled before loading onto SDS-PAGE.
After transferring and blocking of the nonspecific protein-binding
sites with 3% dry milk in TBS, the nitrocellulose membrane was
incubated with different antibodies at suitable dilutions (1:500
dilution of aFGF antibody, R & D Systems, Inc.) in wash buffer
(10 mM Tris-HCl, pH 8.0, 0.15 M NaCl, 0.05% Tween-20) overnight at
4.degree. C. Antigen-antibody complexes were visualized by
incubating the membrane with suitable secondary antibodies and
developing it by ProtoBlot Western Blot AP System (Promega,
Madison, Wis.).
(II) Degradation Test
The intact aFGF peptides were incubated at 37.degree. C. and
54.degree. C., respectively, wherein 54.degree. C. was a self
accelerating decomposition temperature. Then, the samples were
subjected to western blotting. The results for the samples after an
incubation at 37.degree. C. were shown in FIG. 1A, wherein lanes 1
to 3 were the results after 6 hours, 24 hours and 48 hours
incubation, respectively, and lane 4 was the molecular marker, and
the number above each of the bands represented the molecular
weight. The results for the peptide aFGF135 after an incubation at
54.degree. C. during a time period of 120minutes (2 hours) were
shown in FIG, 1B; wherein lanes 1 to 3 were the results after
10minutes, 60 minutes and 120 minutes incubation, respectively, and
lane 4was the molecular marker, and the number above each of the
bands represented the molecular weight.
As shown in FIG. 1A, the peptide aFGF135 maintained its intact
structure at a body temperature (about 37.degree. C.) for at least
48 hours. It indicated that the peptide aFGF135 provided a longer
neural protection effect, and a better stability.
As shown in FIG. 1B, the peptide aFGF135 maintains its intact
structure at 54.degree. C. for at least 1 hour. When the peptide
aFGF135 was incubated at 54.degree. C. for 2 hour, it would fully
degrade rather than transformed into other structure, which may
cause an unpredictable risk of side effects. Subsequently, the
peptide aFGF provided a safe storage or transportation.
Under the same experimental condition, the stability test was
conducted for a commercial recombinant human aFGF having 140 amino
acids ("Promega aFGF", from Promega Corporation). As shown in FIG.
2A, a second band as pointed out by a black arrow was presented in
the band of Promega aFGF; on the contrary, the peptide aFGF135
maintained its structure without degradation. Meanwhile, when added
the samples in a microplate, Promega aFGF appeared evidently white
precipitate but the peptide aFGF135 appeared clear. It indicated
that the peptide aFGF135 had a better stability than commercial
aFGFs.
EXAMPLE 4
.sup.1H--15N-NMR Structural Characterization
NMR spectroscopy is currently the popular techniques capable of
determining the structures of biological macromolecules like
proteins and nucleic acids at atomic resolution. The structural
characterization for the peptide aFGF135 was conducted by High
Field Nuclear Magnetic Resonance Center (Academia Sinica,
Taiwan).
Briefly, the spectra were record at 298 K on Bruker AVANCE 600. C
and N chemical shifts were used in the program TALOS to obtain
backbone torsion angles. Sequence-specific resonance assignments
for the backbone were accomplished using HNCO, HN(CA)CO, HACNCB,
CBCA(CO)NH, HNCA and HN(CO)CA experiments, and side-chain
assignments using .sup.15N-TOCSY-HSQC and .sup.13C-NOESY-HSQC in
combination of .sup.15N-NOESY-HSQC and .sup.13C-NOESY-HSQC. The
backbone spectrum was shown in FIG. 3.
For structure calculation, dihedral angle was obtained by program
TALOS and distance limitation was obtained by .sup.15N-NOESY-HSQC
and .sup.13C-NOESY-HSQC in combination of D2O exchange experiment
to find 26 possible hydrogen bonds. The 3D structural
characterization of the peptide aFGF135 was accomplished by the
program CYANA as shown in FIG. 4A. NMR constraints and structure
calculation statistics for Afgf135 were listed in Table 1.
TABLE-US-00003 TABLE 1 NMR Constraints and Structure Calculation
Statistics for Afgf135.sup.a NOE distance constraints Total 1639
Short range, #i-j#.phi.1 869 Medium range, 1 < #i-j# < 5 206
Long range, 5 < #i-j# 538 Restrained hydrogen bonds 26 Torsion
angle constraints .PHI. 70 .PSI. 76 CYANA target function value
(.ANG..sup.2) 1.26 .+-. 0.31 Ramachandran plot statistics (%)
Residues in most favored regions 65.9 Residues in additional
allowed regions 33.6 Residues in generously allowed regions 0.5
Residues in disallowed regions 0 Root mean square deviation (RMSD)
from the averaged coordinates (.ANG.) Backbone RMSD of full length
1.12 .+-. 0.36 Heavy atom RMSD of full length 1.56 .+-. 0.28
Backbone RMSD of secondary structure.sup.b 0.43 .+-. 0.08 Heavy
atom RMSD of secondary structure.sup.b 0.93 .+-. 0.11 Backbone RMSD
of residues 7-12, 16-30, 0.54 .+-. 0.07 36-53, 58-85, 89-108,
111-131.sup.c Heavy atom RMSD of residues 7-12, 16-30, 1.05 .+-.
0.06 36-53, 58-85, 89-108, 111-131.sup.c .sup.aThe value given
corresponds to the average over the 20 conformers that represent
the solution structure from CYANA .sup.bSecondary structure region
is based on MOLMOL selection: 7-11, 16-21, 25-29, 39-43, 48-53,
59-62, 68-71, 80-85, 89-94, 127-131 .sup.cSelected region
corresponding to region selected in Lozano RM. Et al (Biochemistry,
2; 39(17): 4982-93, 2000)
The 3D structures of the peptide aFGF135 and two known human aFGF
structures were shown in FIG. 4B and FIG. 4C for comparison. The
aFGF having 140 amino acids of SEQ ID NO:6 under PDB Code 1RG8 had
a structure shown in FIG. 4B; and the aFGF having 127 amino acids
of SEQ ID NO:7 under 1DZD had a structure shown in FIG. 4C. The
both are structurally different from the peptide aFGF135 as shown
in FIG. 4A, wherein the N-terminal and C-terminal are buried inside
and lacks a binding loop down left. It indicated that the peptide
aFGF135 with a modified amino acid sequence and a distinct
structure is structurally new and different from known aFGF
peptides.
It will be appreciated by those skilled in the art that changes
could be made to the embodiments described above without departing
from the broad inventive concept thereof. It is understood,
therefore, that this invention is not limited to the particular
embodiments disclosed, but it is intended to cover modifications
within the spirit and scope of the present invention as defined by
the appended claims.
SEQUENCE LISTINGS
1
71135PRTArtificialPeptide derived from Homo sapiens Acid-Fibroblast
Growth Factor (a-FGF) 1Ala Asn Tyr Lys Lys Pro Lys Leu Leu Tyr Cys
Ser Asn Gly Gly His1 5 10 15Phe Leu Arg Ile Leu Pro Asp Gly Thr Val
Asp Gly Thr Arg Asp Arg 20 25 30Ser Asp Gln His Ile Gln Leu Gln Leu
Ser Ala Glu Ser Val Gly Glu 35 40 45Val Tyr Ile Lys Ser Thr Glu Thr
Gly Gln Tyr Leu Ala Met Asp Thr 50 55 60Asp Gly Leu Leu Tyr Gly Ser
Gln Thr Pro Asn Glu Glu Cys Leu Phe65 70 75 80Leu Glu Arg Leu Glu
Glu Asn His Tyr Asn Thr Tyr Ile Ser Lys Lys 85 90 95His Ala Glu Lys
Asn Trp Phe Val Gly Leu Lys Lys Asn Gly Ser Cys 100 105 110Lys Arg
Gly Pro Arg Thr His Tyr Gly Gln Lys Ala Ile Leu Phe Leu 115 120
125Pro Leu Pro Val Ser Ser Asp 130 135228DNAArtificialprimer
2actgaattca tggctgaagg ggaaatca 28330DNAArtificialprimer
3aagaagcttc aatcagaaga gactggcagg 30426DNAArtificialprimer
4ggcatatggc taattacaag aagccc 26533DNAArtificialprimer 5aagagatctc
tttaatcaga agagactggc agg 336140PRTArtificialPeptide derived from
Homo sapiens Acid-Fibroblast Growth Factor (a-FGF) 6Phe Asn Leu Pro
Pro Gly Asn Tyr Lys Lys Pro Lys Leu Leu Tyr Cys1 5 10 15Ser Asn Gly
Gly His Phe Leu Arg Ile Leu Pro Asp Gly Thr Val Asp 20 25 30Gly Thr
Arg Asp Arg Ser Asp Gln His Ile Gln Leu Gln Leu Ser Ala 35 40 45Glu
Ser Val Gly Glu Val Tyr Ile Lys Ser Thr Glu Thr Gly Gln Tyr 50 55
60Leu Ala Met Asp Thr Asp Gly Leu Leu Tyr Gly Ser Gln Thr Pro Asn65
70 75 80Glu Glu Cys Leu Phe Leu Glu Arg Leu Glu Glu Asn His Tyr Asn
Thr 85 90 95Tyr Ile Ser Lys Lys His Ala Glu Lys Asn Trp Phe Val Gly
Leu Lys 100 105 110Lys Asn Gly Ser Cys Lys Arg Gly Pro Arg Thr His
Tyr Gly Gln Lys 115 120 125Ala Ile Leu Phe Leu Pro Leu Pro Val Ser
Ser Asp 130 135 1407127PRTArtificialPeptide derived from Homo
sapiens Acid-Fibroblast Growth Factor (a-FGF) 7Leu Tyr Cys Ser Asn
Gly Gly His Phe Leu Arg Ile Leu Pro Asp Gly1 5 10 15Thr Val Asp Gly
Thr Arg Asp Arg Ser Asp Gln His Ile Gln Leu Gln 20 25 30 Leu Ser
Ala Glu Ser Val Gly Glu Val Tyr Ile Lys Ser Thr Glu Thr 35 40 45Gly
Gln Tyr Leu Ala Met Asp Thr Asp Gly Leu Leu Tyr Gly Ser Gln 50 55
60Thr Pro Asn Glu Glu Cys Leu Phe Leu Glu Arg Leu Glu Glu Asn His65
70 75 80Tyr Asn Thr Tyr Ile Ser Lys Lys His Ala Glu Lys Asn Trp Phe
Val 85 90 95Gly Leu Lys Lys Asn Gly Ser Cys Lys Arg Gly Pro Arg Thr
His Tyr 100 105 110Gly Gln Lys Ala Ile Leu Phe Leu Pro Leu Pro Val
Ser Ser Asp 115 120 125
* * * * *